1. Field of the Invention
The present invention relates to a magnetic recording or reproducing apparatus, and more particularly to such apparatus wherein information is recorded on, or reproduced from, a rotating magnetic recording medium, such as magnetic disk or magnetic drum.
2. Description of the Prior Art
Recently, there has evolved an electronic still camera system which includes an imaging device, such as a solid-state image sensor or an image pickup tube, together with an inexpensive magnetic recording medium of a relatively larger storage capacity, such as a magnetic disk. In such a camera system, a still image of an object is taken to be recorded electronically on a disk, when driven in rotation, and images recorded thereon are reproduced on a separate television system or a printer.
In such an electronic still camera system, the magnetic recording medium may be, for example, a small-sized disk with a diameter on the order of 50 millimeters on which are recorded 50 tracks with a track pitch about equal to 100 .mu.m with the track width and the guard band width being on the order of 50 to 60 .mu.m and 50 to 40 .mu.m, respectively. In the recording or reproducing apparatus, the magnetic disk is rotated at a constant speed of, for example, 3,600 r.p.m. for recording or reproducing video signals at the field or frame rate.
The magnetic disk of such small size and thickness is usually contained in a plastic molded package for usual handling and especially for both recording and reproducing operations. That is, the magnetic disk thus contained in the package is loaded in position in the recording or reproducing device, and driven in rotation for recording or reproduction.
In order to effect high density recording on a magnetic sheet of small size and thickness, a magnetic head is projected beyond a reference or regulation level of the magnetic sheet, which level is defined by the chucking portion of a driving spindle, which is chucked to the core of the magnetic disk to cause rotation of the magnetic sheet, thereby achieving an optimum contact of the magnetic head with the recording surface of the magnetic disk. With the magnetic head protruded in this manner, the magnetic sheet tends to be deviated or retracted in the same direction as that of the magnetic head. Such deviation or retraction of the magnetic sheet is controlled by providing a regulator plate on the opposite side of the sheet with respect to the magnetic head.
In the magnetic recording or reproducing apparatus, the power source is disconnected in many cases from the apparatus whilst the magnetic head is resting on the magnetic sheet. Although the foremost part or chip of the magnetic head shows a larger mechanical strength in connection with sliding contact with the magnetic sheet along the track thereof, it has a lower mechanical strength in a direction normal to the track of the magnetic sheet. The result is that, when the power source is turned off with the head projecting as described above, and the head is radially transported in this state for selecting a desired one of the tracks upon connecting the power source to the apparatus, the head chip is most likely to be injured.